I am going to begin to drain my pool this evening due to high CYA (190)...as I have been discussing here: First Test = Worst Fears Realized...
Based on my CYA level, I assume I need to replace 100% of the water to just start fresh?
Do I just turn on the pump and drain the whole thing at once, or is there any reason i need to do this in stages?
Also, I believe I may have a couple spots of black algae, and assume I should attack those when its drained...but not sure how?
Then once I refill do I just go straight to balancing chems, or do I have to do a period of shock level, etc?